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What is the formula for instantaneous speed?
vinst=d ÷ t
When meausring the instantaneous speed of a car going down a ramp what do you measure as the distance and the time?
- Distance - the length of the mask/card
- Time - the time taken to pass through the light gates
What is the formula for acceleration?
a= v-u ÷ t
- u = initial speed
- v = final speed
What is acceleration measured in?
Acceleration is defined as the rate of change of speed
What three effects can a force have on an object?
- Change the:
What do we use to measure forces?
A spring balance
What are forces measured in?
Name three common forces
- Air resistance
- Muscle force
- Engine Force
What is friction caused by?
The microscopic bumps on any surface
How do we decrease friction?
- Make the material smoother (sand it)
- Lubricate it
- Try to make the motion rolling (like the bearings on axels)
What is the formula for weight?
What is the mass of an object?
The amount of matter there is in an object (measured in kg)
What is the weight of an object?
The force of gravity pulling down on the mass of an object (measured in N)
What is the gravitational field strength on Earth?
How do you work out a vehicle's stopping distance?
Stopping distance = thinking distance + braking distance
What can affect the thinking distance?
- The speed of the vehicle (the greater the speed the greater the distance before the brakes are applied)
- The reaction time of the driver (the slower a driver's reactions the greater the distance travelled before the brakes are applied. Drinking, drugs and tiredness will increase this time)
What can affect the braking distance?
- The mass of the vehicle
- The speed of a vehicle
- The braking force
- Fictional forces
What is Newton's first law?
If the forces on an object are balanced then the object remains stationary or at a constant speed
What is Newton's second law?
The acceleration of an object varies directly with the unbalanced force and inversely with its mass
What is the formula for unbalanced forces?
uF = ma
What is energy measured in?
What is Work done?
Work done is when energy is transferred
What is the formula for work done?
Ew = Fd
What is kinetic energy?
The energy of moving objects
What is the formula for kinetic energy?
Ek = 0.5mv2
What is the formula for potential energy?
Ep = mgh
What is power measured in?
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